Apparatus for amplifying musical tones



March 19, 1935.

I w. w. NELSON APPARATUS FOR AMPLIFYING MUSICAL TONES Filed Jan. 28, 1935 M INVEN HJR:

Patented Mar. 19, 1935 UNITED STATES PATENT OFFICE APPARATUS FOR AIHPLIFYING MUSICAL TONES William W. Nelson, Newton, Mass.

Application January 28, 1933, Serial No. 654,024

4 Claims.

purpose employing a diaphragm transmitter for transmitting the tones from the string instrument to an electrical reproducer. principal objections to such an apparatus is that the reproducer must be positioned a considerable distance, or even in a separate .room from the string instrument and transmitter to avoid squeaking and distortion of the musical tones. Consequently, it is diflicult and often impossible for the player of the instrument to control the volume of amplification of the musical tones.

It is an object of the present invention. to provide an apparatus for this purpose which will overcome the above mentioned dimculty.

' A further object of the invention is the provision of an apparatus for such purpose having a pick up device or transmitter adapted to be mounted directly in any string instrument without essential modification of either the apparatus or the string instrument.

Another object of the invention resides in a transmitter having associated therewith resilient means for yieldingly urging the transmitter in a direction to press its stylus against the sounding board or other element receiving the vibrations of the strings, to thereby maintain the proper pressure of the stylus against the vibrating element.

A still further object of the invention resides in manually operable means for adjusting the transmitter within the string instrument to bring its stylus into engagement with the sounding board, and to cause the resilient means to act with the required force upon the transmitter to secure the proper pressure of the stylus against the sounding board.

The invention will be more clearly understood from the following description in conjunction with the accompanying drawing: in which,

Fig. 1 is an elevational view, partly broken away, of a string instrument having associated therewith an apparatus embodying the invention;

Fig. 2 is a detail plan view of a portion of the apparatus embodying the invention;

Fig. 3 is a longitudinal sectional elevational view of a portion of the string instrument showing the relation thereto of the portion of the apparatus of the invention illustrated in Fig. 2, and

Fig. 4 is a top plan view of part of the electromagnetic pick up device, having the cover broken away.

Before explainingin detail the present invention it is to be understood that the invention is not limited in its application to the details of One of the construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art.

In the accompanying drawing a string instrument is illustrated comprising a head connected by a neck 11 to a body 12. Fitted upon the body 12 in the usual manner is a sounding board 13 having an opening 14 therein, usually of circular shape. The usual strings 8 are stretched over a bridge 9 supported in the usual manner upon the sounding board 13. In accordance with the invention a support 15 is detachably mounted within the body 12 and is provided with a pair of spaced legs 16 adapted to engage the underside of the sounding board 13 adjacent diametrically opposite points of the opening 14. A clamping bar 17 straddles the opening 14 and engages the top surface of the sounding board over the legs 16 and is connected to the support 15 as by screws 18 passing through the opening 14.

An electromagnetic pick up device or transmitter 20 is pivotally or yieldingly mounted upon the support 15 near one end thereof as by a screw 21 having threaded engagement with the device 20 and having a rotative bearing in one of a plurality of openings 22 provided in the support 15.

The electromagnetic pick up or transmitter 20 may be of any well known or suitable construction which avoids the use of the objectionable diaphragm above referred to, and as shown comprises a base plate 20' to which the electromagnetic parts are secured and these parts are protected by a hollow cover or housing 20" secured to the plate 20'. Fastened to the base plate 20 within the housing 20 is a permanent or horseshoe magnet M, and extending across the ends of this magnet is the bar M which is partly cut away to provide the poles m and an opening to receive the magnetic coil C.

The pick up device is provided with a stylus or needle 23 which is pivotally supported by the pick up device for slight vibratory movement relative thereto, and in the construction shown the means for pivotally supporting the stylus comprises a cylindrical post or hub 23" that is mounted in a drill hole extending transversely of the bar M between an outer edge thereof and the coil C. This hub has a flat rearwardly extending arm 23' adapted to extend through the centre of the coil to vibrate between the poles m and the outer end of this arm extends through a slot in a pad of rubber R which acts to dampen the vibrations of the arm and hold it away from a pole. Extending frontwardly from the hub 23" is the hollow arm 23" adapted to receive a laterally bent portion of the stylus 23 and this portion of the stylus is clamped in the hollow arm 23" by a screw 8 extending axially of the hub 23". The hub 23" is preferably insulated from the bar M by a thin piece of sheet rubber 1 that is placed about the hub throughout its length; see Fig. 4 in which the clamping screw s has been omitted to better show this rubber sheet.

The magnetic coil C may be connected by conduotors 25 with a reproducer 26 of any preferred or well known construction and the reproducer may be supplied with amplifying energy from an electric circuit (not shown). The arrangement is such that vibrations of the arm 23' of the stylus between the poles 11!. cause variations to be produced in the current of the electric coil associated with the magnet M.-

A stud 30 is threaded in one of a plurality of threaded openings 31 in the support 15 and is provided with a transversely extending threaded opening adapted to receive the threaded portion of a rod 32 having at one end a knurled operating knob 33. The rod 32 extends through a slot 34 in an ear 35 projecting from the device 20. The other end of the rod 32 is provided with a head 36 rigid therewith. The ear 35 is held against the head 36 by a spring 37 surrounding the rod 32 with one end engaging ear 35 and its other end engaging a collar 38 secured upon the rod 32. As a result of this construction the maximum pressure upon the stylus 23 is controlled by the tension of the spring 37, and the pick up device 20 is supported for yielding movement relative to the sounding board 13 or other part engaged by the stylus 23.

In accordance with the invention the support 15 and the electromagnetic device 20 pivotally carried thereby are arranged so that they may be inserted readily through the opening 14 and be clamped readily within the string instrument.

. The rod 32 is adiustably mounted upon the support 15 so that its operating knob 33 is conveniently accessible from outside the instrument through the opening 14. The post 30 and the pivot screw 21 are mounted in the openings 31 and 22, respectively, which will position the needle 23 of the device 20 so that its outer end may engage the'sounding board directly under the bridge 9. The spring 37 is adapted to exert a resilient pressure upon the device 20 so as to urge the free end of the needle 23 toward the sounding board 13. The amount of pressure exerted by the needle 23 upon the sounding board may be conveniently adiusted by inserting ones fingers through the opening 14 and turning the rod 32.

Thus, it will be noted that the apparatus 01' the invention embodies a pick up or transmitting device which can be readily mounted upon any string instrument by merely inserting the same through the opening in the sounding board and clamping the device within the instrument. The proper relation between the needle 23 and the sounding board can be obtained initially and any adjustments necessary to secure the proper pressure of the stylus against the sounding board can be made by merely turning the rod 32. The apparatus of the invention enables the player of the string instrument to control the volume of the reproduced musical tones because the reproducer can be positioned close to the player and string instrument without danger of causing squeaking or distortion of the musical tones.

It will also be seen that since the pick up device 20 is provided with yielding or resilient means for urging the pick up device in a direction to press its stylus against the sounding board, the stylus is permitted to yield to accommodate itself to expansion and contraction of the sounding board due to climatic conditions or other changes, and in this manner the proper pressure of the stylus against the sounding board is automatically secured.

What I claim is:

1. In an apparatus for producing musical tones, a musical instrument having a bridge engaging strings stretched thereover, the combination therewith of a support within the instrument, an electromagnetic pick up pivotally mounted on said support, said pick up having a needle adapted to receive the vibrations imparted to' said bridge by said strings, a member adjustably carried by said support, and operative connections between said member and pick up including resilient means adapted to urgesaid needle toward said bridge.

2. In an apparatus for producing musical tones, a string musical instrument having a sounding board, the combination therewithof a support within the instrument, an electromagnetic pick up pivotally mounted on said support, said pick up having a needle adapted to receive the vibrations imparted to said sounding. board, a member adjustably carried by said support, and operative connections between said member and pick up including resilient means adapted to urge said needle toward said sounding board.

3. In an apparatus for producing musical tones,

a musical instrument comprising a sounding board having an opening therein, a bridge supported on said sounding board, and strings stretched over and engaging said bridge, the combination therewith of a support insertable through said opening, an electromagnetic pick up pivotally mounted upon said support, said electromagnetic pick up having a needle adapted to engage said sounding board, a member adjustably carried by said support, operative connections between said member and electromagnetic pick up including resilient means adapted to urge said needle toward the sounding board, and means for clamping said support within said instrument so that said member is accessible for adjustment through said opening.

4. In an apparatus for producing musical tones comprising a musical instrument having an element that responds to the vibrations thereof, the combination therewith of a support secured to said instrument, an electric pick up device mounted on the support and movable relatively to said vibratory element, said pick up device having magnetic poles, a stylus loosely mounted thereon to extend in part between said poles and in part to receive-the vibrations of said element, and yielding means assisting in maintaining said stylus in proper spaced relationship to said poles, and resilient means for shifting the position of said pick up device in a direction to hold its stylus against the vibratory element and change the position of said part of the stylus extending between said poles with relation thereto.

WILLIAM W. NELSON. 

